The present invention generally relates to angular position sensors and, more particularly, to apparatus for sensing an angular position of a wheel hub of a steerable wheel of a vehicle about a steering axis thereof, through a kingpin supporting the wheel hub.
It is a well known, common practice to detect and monitor angular position of steerable wheels of vehicles relative to a reference angular position, such as a straight ahead position, for purposes such as providing a steering input to an automatic guidance system for the vehicle, a differential lock system, and the like. Reference in this regard, Wilks et al. U.S. Pat. No. 5,366,042, issued Nov. 22, 1994 to ZF Friedrichshafen AG of Germany, which discloses a device for detecting different steering angles of a driven wheel of an axle for a motor vehicle, utilizing multiple sensors disposed in radial bores in a housing supporting an axle kingpin for rotation about a steering axis. Reference also Sollbach et al. U.S. Pat. No. 4,775,026, issued Oct. 4, 1988 to Zahnradfabrik Friedrichshafen AG of Germany, which discloses actuation of a differential lock utilizing an inductive switch or potentiometer in the area of angle dependent steering elements held fast in an axle housing of a vehicle for determining steering angle. A particular embodiment of this latter referenced patent mounts a rotary potentiometer in a housing integrated with a pivot bearing, and includes an adjusting pin held in positive engagement with the potentiometer shaft by means of a screwdriver slot and expansion spring for allowing joint rotation thereof, the adjusting pin being clampable in place inside a hollow screw on the steering pivot such that the potentiometer shaft is reliably taken along rotationally with rotation of the pivot. It is recited that small angular errors or normally occurring axial displacements of the foregoing arrangement cause no damage to the potentiometer.
Addressing observed shortcomings of the referenced devices, the former device requires multiple sensors and conductive paths for communication with a signal processing unit for sensing angular position so as to be disadvantageous costwise. A shortcoming of the latter referenced arrangement is only a limited capability for compensating for or overcoming misalignment of the potentiometer or other sensor relative to the steering pivot and variances in the distances therebetween resulting from manufacturing and assembly tolerances, damage, and wear. Another shortcoming is the location of the potentiometer or other sensor in a difficult to access location within the axle housing, thus requiring substantial disassembly for accessing the potentiometer for service and replacement.
Accordingly, it would be desirable to provide apparatus for sensing an angular position of a steerable wheel arrangement of a vehicle about a steering axis thereof, which overcomes the shortcomings discussed above.
According to the invention, apparatus for sensing an angular position of a steerable wheel of a vehicle, such as a work machine or the like, about a steering axis thereof, is disclosed. The apparatus includes a support frame having an upper arm and a lower arm projecting therefrom defining a space therebetween, the lower arm having a passage therethrough communicating with the space, the steering axis extending through the space and the passage; a wheel hub being located in the space for supporting the wheel, the steering axis extending through a predetermined bottom axial surface portion of the wheel hub; a lower kingpin mounted in the passage through the lower arm and supporting the wheel hub in the space for rotation about the steering axis, the lower kingpin including an axial passage therethrough extending between an upper axial opening facing the bottom axial surface portion of the wheel hub and a bottom opening; a sensor mounted in connection with the bottom opening of the lower kingpin, the sensor including an element rotatable about a rotational axis, the sensor being operable for sensing a rotational position of the rotatable element about the rotational axis; and a pin extending through the axial passage through the kingpin and having a first end pivotably connected to the wheel hub for rotation therewith, and a second end connected to the element for rotating the element when the wheel hub is rotated about the steering axis.